This invention relates to ball joints of the type utilized in steering linkages of automotive vehicles. More particularly, this invention relates to the socket bearing portion of ball and socket joints of such linkage systems.
A major problem relating to ball and socket joints is retention of lubrication within the socket-ball interface during the useful life of the joint. Numerous methods have been utilized to obtain satisfactory lubrication of such joints. For example, networks of lubrication grooves, disposed in either the ball or the socket, have been used to distribute lubrication about the ball-socket interface. Such groove designs, however, remain generally deficient, some even permitting lubrication flow out of the interface.
In addition, the need for materials having high lubricity for maximum joint life tends to dictate the use of synthetic nonmetallic bearing materials. The grooves formed in such materials tend to deteriorate under a "cold flow" process wherein the grooves plastically collapse under the bearing loads. This latter problem is perhaps exacerbated by the use of "squared" edges common to typical lubrication grooves. To the extent that sharp edges give rise to higher stresses per given bearing load, squared-edged grooves are inherently weaker. "Abrupt" or sharp edges also tend to scrape lubrication off of the ball rather than to facilitate its transfer onto the ball. This can be a particular problem with a joint which oscillates within a range of only five to eight degrees.
What is needed is a design which would enhance lubrication movement within the ball-socket interface while restricting the loss of lubricant from the interface during the useful life of the joint. In addition, a lubrication groove design is needed which is stronger under the bearing loads imposed upon todays joints. Finally, a design is also needed which would inherently facilitate lubrication transfer from groove to socket-ball contact areas.